1 . Technical Field
This application relates to the technology of precision gas injection for gas-assisted reactions in irradiation beam instruments.
2 . Background Art
Irradiation beam instruments include those using charged-particle beams, such as a scanning electron microscopes (SEM) or focused-ion beam (FIB) microscopes, or instruments using beams of light, such as scanning laser microscopes, or instruments that combine these technologies, such as triple beam SEM/FIB/laser microscopes. The gas-assisted reactions include gas-assisted deposition of fine structures using chemical vapor-deposition (CVD) techniques or etch reactions in which the precursor gas is directed onto a sample surface where one or more irradiation beams has also been directed.
The rates of precursor flow and carrier gas flow in a system affect the rate of beam-assisted reactions, and thus the effectiveness of the deposition or etch process. We disclose methods and apparatus for improved control of these variables, with the resulting advantages of more precise work on finer structures than is currently available. This reduces the waste of expensive precursor materials between operation cycles.
Also, the lines and chambers in a precursor delivery system are preferably purged by some inert gas between the flows of different precursors. Existing systems rely on venting the lines and chambers immediately to the FIB vacuum chamber. It would be highly desirable to shorten the time needed to purge a precursor delivery system while also avoiding contamination of the system vacuum caused by venting the precursor delivery system through the instrument vacuum chamber.